Method for stabilizing retinoic acid precursors and a skin benefit composition with stabilized retinoic acid precursors

ABSTRACT

A method for stabilizing retinoic acid precursors and a skin benefit composition with stabilized retinoic acid precursors are described. The composition has a retinoic acid precursor and a resorcinol to impede oxidation of the precursor in situ in the composition.

FIELD OF THE INVENTION

The present invention is directed to a method for stabilizing retinoicacid precursors and a skin benefit composition comprising suchstabilized precursors. More particularly, the invention is directed to amethod and skin benefit composition that use a skin benefit agentcomprising a resorcinol and/or derivative thereof to prevent in situoxidation of retinoic acid precursors. The compositions of thisinvention are surprisingly stable, free of malodour and discoloration,and do not irritate skin upon topical application.

BACKGROUND OF THE INVENTION

Many consumers find it desirable to deliver skin benefits via methodsthat rely on the application of topical compositions. This is especiallytrue when consumers wish to look younger by reducing facial lines andwrinkles as well as blotchy color marks on the skin.

Minimizing cutaneous aging, both intrinsic and from photoaging, is oftenattempted with compositions with retinoic acid precursors. While suchcompositions can provide benefits to skin, instability of suchprecursors, typically the result of in situ oxidation, results inpremature formation of retinoic acid as well as other oxidised compoundsin packaged compositions and prior to application. This results in aproduct that may irritate a consumer's skin shortly after application,possesses a malodour and/or is tainted with discoloration. It could evenresult in a non-stable composition with oxidised compounds that do notnecessarily have a positive impact on skin.

It is of increasing interest to develop a stable skin benefitcomposition that is suitable to provide benefits to skin and has reducedamounts of premature retinoic acid precursor oxidation.

This invention, therefore, is directed to a composition with stabilizedretinoic acid precursors that have been stabilized with a skin benefitagent comprising a resorcinol. The composition of the present inventionsurprisingly can be topically applied without causing skin irritation,free of malodour and discoloration while simultaneously deliveringexcellent skin benefits. The inventive composition allows for betterpenetration of retinoic acid precursors into skin so that the same mayconvert to retinoic acid after penetration and for enhanced efficacy.

ADDITIONAL INFORMATION

Efforts have been disclosed for making formulations to treat skin. InU.S. Pat. No. 4,826,828, retinol comprising compositions with volatilesilicones are described.

Still other efforts have been disclosed for making formulations to treatskin. In U.S. Pat. No. 8,299,127, a method and composition for evenlyapplying water soluble actives to skin is described.

Even other efforts have been disclosed for making formulations to treatskin. In EP0093770B1, compositions with retinoids and minoxidil forenhancing scalp hair growth are described.

U.S. Pat. Nos. 6,863,897, 6,869,598, and 6,858,217 all describe topicalcompositions with resorcinols.

None of the additional information above describes a composition withstabilized retinoic acid precursors that have been stabilized with askin benefit agent comprising resorcinol.

SUMMARY OF THE INVENTION

In a first aspect, the present invention is directed to a compositioncomprising:

-   -   (a) a retinoic acid precursor;    -   (b) a skin benefit agent comprising resorcinol and/or a        derivative thereof; and    -   (c) a cosmetically acceptable carrier        wherein the skin benefit agent impedes oxidation of the retinoic        acid precursor and the retinoic acid precursor and the skin        benefit agent comprising resorcinol and/or a derivative thereof        are present at a weight ratio from 0.2 to 4 to 4 to 0.2,        including all weight ratios subsumed therein.

In a second aspect, the present invention is directed to a method ofimpeding in situ oxidation of a retinoic acid precursor.

All other aspects of the present invention will readily become apparentupon considering the detailed description and examples which follow.

Skin, as used herein, is meant to include skin on the feet, face, neck,chest, back, arms, hands, legs, buttocks and scalp (including hair). Thecomposition of this invention includes creams, lotions, balms, serums,deodorants and antiperspirants, shampoos, conditioners, bars and liquidwash products. In a preferred embodiment, the composition of thisinvention is a leave-on composition like a leave-on cream or lotion.

Skin benefit agent comprising resorcinol and/or a derivative thereof(“SBA”) means an agent that is at least 25 percent by weight resorcinoland/or derivative thereof, and preferably 40 to 95 percent resorcinoland/or derivative thereof, and most preferably, all resorcinol and/orits derivatives. Skin benefit agent includes an agent that may beformulated in the composition of this invention to improve a skincharacteristic. Retinoic acid precursor (“RAP”) means a component that,when oxidized, can convert to retinoic acid. Examples of such acomponent include retinol, retinal, retinyl propionate, retinylpalmitate, hydroxyanasatil retinoate (i.e., Retextra®) mixtures thereofor the like. More preferred retinoic acid precursors in the context ofthe invention are retinal, retinyl propionate, retinyl palmitate,hydroxyanasatil retinoate (i.e., Retextra®) and mixtures thereof. Evenmore preferred are retinyl propionate, hydroxyanasatil retinoate (i.e.,Retextra®) and mixtures thereof. Most preferred is hydroxyanasatilretinoate (i.e., Retextra®). Unless explicitly stated otherwise, allranges described herein are meant to include all ranges subsumedtherein. The term comprises is meant to encompass the terms consistingessentially of and consisting of. For the avoidance of doubt, acomposition comprising retinoic acid precursor, resorcinol and acosmetic carrier is also meant to include a composition consistingessentially of and a composition consisting of the same. All percentagesused herein are meant to be by weight unless stated otherwise. Thecomposition of this invention is meant to include a skin benefitcomposition suitable for sale and application (e.g., topically) by aconsumer. The composition of the invention which is suitable to providebenefit to skin can be an emulsion or a composition that is free ofwater and emulsifier. Free of malodour and discoloration meanssurprisingly not any worse than control deplete of SBA. Stable, as usedherein, means a measurable decrease in retinoic acid precursor oxidationwithin the composition (i.e., in situ). Resorcinol derivative means atleast one H on the ring structure and/or on a hydroxy group of theresorcinol replaced with an alkyl group. The preferred RAPs used in thisinvention are 4-substituted resorcinols.

Except in the operating and comparative examples, or where otherwiseexplicitly indicated, all numbers in this description indicating amountsor ratios of materials or conditions and/or physical properties ofmaterials and/or use are to be understood as modified by the word“about”.

DETAILED DESCRIPTION OF THE INVENTION

The only limitation with respect to the retinoic acid precursors thatmay be used in the compositions of this invention is that the same aresuitable for formulating into a composition that may be applied to humanskin. Illustrative examples of the retinoic acid precursors that may beused in this invention include those represented by the formula

where each R is independently a hydrogen or a C₁₋₆ alkyl group and X is

and further where each R′ is hydrogen or a C₁-C₃ alkyl and n is aninteger from 0 to 16 (preferably from 6 to 16, more preferably from 1 to5).

Preferably the retinoic acid precursor comprises, more preferably is,retinol, retinal, retinyl propionate, retinyl palmitate or a mixturethereof. Even more preferably, the retinoic precursor comprises, morepreferably is, retinyl proprionate, retinyl palmitate or a mixturethereof.

Still another retinoic acid precursor suitable for use is hydroxanasatilretinoate made commercially available under the name Retextra® assupplied by Molecular Design International. The same may be used in amixture with the precursors described herein.

Typically the amount of retinoic acid precursor used in the compositionsof this invention is from 0.001 to 10%, and preferably, from 0.01 to 6%,and most preferably, from 0.05 to 3.5%, based on total weight of thecomposition and including all ranges subsumed therein.

Regarding the skin benefit agent comprising resorcinol and/or derivativethat may be used, the same is limited only to the extent that it issuitable for formulating in compositions, especially topicalcompositions.

Illustrative examples of the types of SBAs that may be used in thisinvention include those represented by the formula

wherein each R″ is independently hydrogen, or C₁₋₆ alkyl and R′″ ishydrogen or a C₁₋₁₈ linear or branched alkyl.

Often, R″ is hydrogen and the SBA is a resorcinol derivative like4-methyl resorcinol, 4-ethyl resorcinol, 4-propyl resorcinol, 4-butylresorcinol, 4-pentyl resorcinol, 4-hexyl resorcinol, 4-heptylresorcinol, 4-octyl resorcinol, 4-isopropyl resorcinol, mixtures thereofor the like. It is preferred that the SBA in the context of theinvention is 4-methyl resorcinol, 4-ethyl resorcinol, 4-propylresorcinol, 4-butyl resorcinol, 4-pentyl resorcinol, 4-hexyl resorcinol,4-heptyl resorcinol, 4-octyl resorcinol, 4-isopropyl resorcinol,mixtures thereof or the like. More preferably, the SBA is 4-methylresorcinol, 4-ethyl resorcinol, 4-propyl resorcinol, 4-butyl resorcinol,4-pentyl resorcinol, 4-heptyl resorcinol, 4-octyl resorcinol,4-isopropyl resorcinol, mixtures thereof or the like. Even morepreferably, the SBA is 4-ethyl resorcinol, 4-butyl resorcinol, 4-hexylresorcinol, 4-isopropyl resorcinol, mixtures thereof or the like. Apreferred SBA is 4-ethyl resorcinol. This preferred SBA or SBAs arepreferably combined with the retinoic acid precursors preferred in thecontext of the invention that are retinal, retinyl propionate, retinylpalmitate, hydroxyanasatil retinoate (i.e., Retextra®) and mixturesthereof. Even more preferred are retinyl propionate, hydroxyanasatilretinoate (i.e., Retextra®) and mixtures thereof. More preferred areretinyl propionate, retinyl palmitate and mixtures thereof. Alsohydroxyanasatil retinoate (i.e., Retextra®) can be a preferred RAP.

Typically, the amount of SBA used is from about 0.001 to 10%, andpreferably, from 0.01 to 6%, and most preferably, from 0.1 to 3.5%,based on total weight of the composition and including all rangessubsumed therein.

The weight ratio of RAP to SBA is from 0.2:4 to 4:0.2, and preferably,from 0.2:3 to 3:0.2, and most preferably, from 0.25:1 to 1:0.25,including all ratios subsumed therein.

The compositions of this invention can have as cosmetically acceptablecarriers non-polar liquids like oils comprising the RAP and SBA presentat ratios as described herein. Alternatively, such non-polar liquidscomprising the RAP and SBA can be used as the oil phase when thecomposition is an emulsion. The weight ratio of RAP to SBA can also befrom 0.5:4.0 to 4.0:0.5.

When the compositions of the present invention are emulsions, they willtypically include cosmetically acceptable carrier components in additionto non-polar liquid with RAP and SBA as described herein. In an oftenpreferred embodiment the RAP and SBA are added as a pre-mix with anon-polar liquid to prepare the composition of this invention. Water isthe most preferred additional carrier. Amounts of water may range from 1to 99%, and preferably, from 5 to 90%, and most preferably, from 35 to80%, and optimally, from 40 to 75% by weight, based on total weight ofthe composition and including all ranges subsumed therein. Ordinarilythe compositions of this invention will be water and oil emulsions, mostpreferably, of the oil-in-water variety. Water-in-oil emulsions, andespecially, those generally classified as water-in-oil and high internalphase emulsions are, however, an option. Illustrative examples of thehigh internal phase emulsions suitable to carry the SBA and RAP of thisinvention are described in commonly owned U.S. Patent ApplicationPublication No. 2008/0311058 and U.S. Pat. No. 8,425,882, thedisclosures of which are incorporated herein by reference.

Other cosmetically acceptable carriers suitable for use (with or withoutwater and also for use to combine RAP and SBA) in this invention mayinclude mineral oils, silicone oils, esters, and alcohols. Amounts ofthese materials may collectively range from 0.1 to 99%, and preferably,from 0.1 to 45%, and most preferably, from 1 to 20% by weight of thecomposition of this invention, including all ranges subsumed therein.

Silicone oils may be divided into the volatile and non-volatile variety.The term “volatile” as used herein refers to those materials which havea measurable vapor pressure at ambient temperature. Volatile siliconeoils are preferably chosen from cyclic or linear polydimethylsiloxanescontaining from 3 to 9, and preferably, from 4 to 5 silicon atoms.

Linear volatile silicone materials generally have viscosities of lessthan 5 centistokes at 25° C. while cyclic materials typically haveviscosities of less than about 10 centistokes.

Nonvolatile silicone oils useful as carrier material include polyalkylsiloxanes, polyalkylaryl siloxanes and polyether siloxane copolymers.The essentially non-volatile polyalkyl siloxanes useful herein include,for example, polydimethylsiloxanes (like dimethicone) with viscositiesof from 5 to 100,000 centistokes at 25° C.

An often preferred silicone source is a cyclopentasiloxane anddimethiconol solution.

Among suitable esters are:

-   -   (I) Alkenyl or alkyl esters of fatty acids having 10 to 20        carbon atoms like isopropyl palmitate, isopropyl isostearate,        isononyl isonanonoate, oleyl myristate, isopropyl myristate,        oleyl stearate, and oleyl oleate;    -   (2) Ether-esters such as fatty acid esters of ethoxylated fatty        alcohols;    -   (3) Polyhydric alcohol esters such as ethylene glycol mono- and        di-fatty acid esters, diethylene glycol mono- and di-fatty acid        esters, polyethylene glycol (200-6000) mono- and di-fatty acid        esters, propylene glycol mono- and di-fatty acid esters,        polypropylene glycol 2000 monooleate, polypropylene glycol 2000        mono stearate, ethoxylated propylene glycol monostearate,        glyceryl mono- and di-fatty acid esters, polyglycerol poly-fatty        esters, ethoxylated glyceryl mono-stearate, 1,3-butylene glycol        monostearate, 1,3-butylene glycol distearate, polyoxyethylene        polyol fatty acid ester, sorbitan fatty acid esters, and        polyoxy-ethylene sorbitan fatty acid esters;    -   (4) Wax esters such as beeswax, spermaceti, myristyl myristate,        stearyl stearate; and    -   (5) Sterol esters, of which soya sterol and cholesterol fatty        acid esters are examples thereof.

Often, oils such as caprylic capric triglyceride are preferred ascarriers.

Emulsifiers may be present in the compositions of the present invention.Total concentration of the emulsifier may range from about 0.1 to 40%,and preferably, from 1 to 20%, and most preferably, from 1 to 5% byweight of the composition, including all ranges subsumed therein. Theemulsifier may be selected from the group consisting of anionic,nonionic, cationic and amphoteric actives. Particularly preferrednonionic actives are those with a C₁₀-C₂₀ fatty alcohol or acidhydrophobe condensed with from about 2 to about 100 moles of ethyleneoxide or propylene oxide per mole of hydrophobe; C₂-C₁₀ alkyl phenolscondensed with from 2 to 20 moles of alkylene oxide; mono- and di-fattyacid esters of ethylene glycol; fatty acid monoglyceride; sorbitan,mono- and di-C₈-C₂₀ fatty acids; and polyoxyethylene sorbitan as well ascombinations thereof. Alkyl polyglycosides and saccharide fatty amides(e.g. methyl gluconamides) are also suitable nonionic emulsifiers.

Preferred anionic emulsifiers include alkyl ether sulfate andsulfonates, alkyl sulfates and sulfonates, alkylbenzene sulfonates,alkyl and dialkyl sulfosuccinates, C₈-C₂₀ acyl isethionates, C₈-C₂₀alkyl ether phosphates, alkyl ether carboxylates and combinationsthereof.

Cationic emulsifiers that may be used include, for example,almitamidopropyltrimonium chloride, distearyldimonium chloride andmixtures thereof. Useful amphoteric emulsifiers include cocoamidopropylbetaine, C₁₂-C₂₀ trialkyl betaines, sodium lauroamphoacetate, and sodiumlaurodiamphoacetate or a mixture thereof.

Other generally preferred emulsifiers include glyceryl stearate, glycolstearate, stearamide AMP, PEG-100 stearate, cetyl alcohol as well asemulsifying/thickening additives like hydroxyethylacrylate/sodiumacryloyldimethyl taurates copolymer/squalane and mixtures thereof.

Preservatives can desirably be incorporated into the compositions ofthis invention to protect against the growth of potentially harmfulmicroorganisms. Suitable traditional preservatives for compositions ofthis invention are alkyl esters of para-hydroxybenzoic acid. Otherpreservatives which have more recently come into use include hydantoinderivatives, propionate salts, and a variety of quaternary ammoniumcompounds. Cosmetic chemists are familiar with appropriate preservativesand routinely choose them to satisfy the preservative challenge test andto provide product stability. Particularly preferred preservatives areiodopropynyl butyl carbamate, phenoxyethanol, 1,2-octanediol,ethylhexylglycerine, hexylene glycol, methyl paraben, propyl paraben,imidazolidinyl urea, sodium dehydroacetate and benzyl alcohol. Thepreservatives should be selected having regard for the use of thecomposition and possible incompatibilities between the preservatives andother ingredients in the emulsion. Preservatives are preferably employedin amounts ranging from 0.01% to 2% by weight of the composition,including all ranges subsumed therein. Combinations of 1,2-octanedioland phenoxyethanol, or iodopropynyl butyl carbamate and phenoxyethaolare preferred, with phenoxyethanol making up from 35 to 65% by weight ofthe total weight of the preservative combination with thephenoxyethanol.

Thickening agents may optionally be included in compositions of thepresent invention. Particularly useful are the polysaccharides. Examplesinclude starches, natural/synthetic gums and cellulosic s.Representative of the starches are chemically modified starches such assodium hydroxypropyl starch phosphate and aluminum starchoctenylsuccinate. Tapioca starch is often preferred. Suitable gumsinclude xanthan, sclerotium, pectin, karaya, arabic, agar, guar,carrageenan, alginate and combinations thereof. Suitable cellulosicsinclude hydroxypropyl cellulose, hydroxypropyl methylcellulose,ethylcellulose and sodium carboxy methylcellulose. Synthetic polymersare yet another class of effective thickening agent. This categoryincludes crosslinked polyacrylates such as the Carbomers,polyacrylamides such as Sepigel 305 and taurate copolymers such asSimulgel EG and Arlstoflex AVC, the copolymers being identified byrespective INCI nomenclature as Sodium Acrylate/Sodium AcryloyldimethylTaurate and Acryloyl Dimethyltaurate/Vinyl Pyrrolidone Copolymer.Another preferred synthetic polymer suitable for thickening is anacrylate-based polymer made commercially available by Seppic and soldunder the name Simulgel INS100.

Amounts of the thickener, when used, may range from 0.001 to 5%, andpreferably, from 0.1 to 2%, and most preferably, from 0.2 to 0.5% byweight of the composition and including all ranges subsumed therein.

Fragrances, fixatives and abrasives may optionally be included incompositions of the present invention. Each of these substances mayrange from about 0.05 to about 5%, preferably between 0.1 and 3% byweight.

To enhance skin moisturization, cationic ammonium compounds mayoptionally be used in the compositions of this invention to enhancemoisturization. Such compounds include salts of hydroxypropyltri (C₁-C₃alkyl) ammonium mono-substituted-saccharide, salts of hydroxypropyltri(C₁-C₃ alkyl) ammonium mono-substituted polyols, dihydroxypropyltri(C₁-C₃ alkyl) ammonium salts, dihydroxypropyldi (C₁-C₃ alkyl)mono(hydroxyethyl) ammonium salts, guar hydroxypropyl trimonium salts,2,3-dihydroxypropyl tri (C₁-C₃ alkyl or hydroxalkyl) ammonium salts ormixtures thereof. In a most preferred embodiment and when desired, thecationic ammonium compound employed in this invention is the quaternaryammonium compound 1,2-dihydroxypropyltrimonium chloride. If used, suchcompounds typically make up from 0.01 to 30%, and preferably, from 0.1to 15% by weight of the composition.

When cationic ammonium compounds are used, additional preferredadditives for use with the same are moisturizing agents such assubstituted ureas like hydroxymethyl urea, hydroxyethyl urea,hydroxypropyl urea; bis(hydroxymethyl) urea; bis(hydroxyethyl)urea;bis(hydroxypropyl)urea; N, N′-dihydroxymethyl urea; N,N′-di-hydroxyethyl urea; N, N′-dihydroxypropyl urea; N, N,N′-tri-hydroxyethyl urea; tetra (hydroxymethyl)urea;tetra(hydroxyethyl)urea; tetra (hydroxypropyl)urea;N-methyl-N′-hydroxyethyl urea; N-ethyl-N, N—N′-hydroxyethyl urea;N-hydroxypropyl-N′-hydroxyethyl urea and N, N′-dimethyl-N-hydroxyethylurea or mixtures thereof. Where the term hydroxypropyl appears, themeaning is generic for either 3-hydroxy-n-propyl, 2-hydroxy-n-propyl,3-hydroxy-i-propyl or 2-hydroxy-i-propyl radicals. Most preferred ishydroxyethyl urea. The latter is available as a 50% aqueous liquid fromthe National Starch & Chemical Division of ICI under the trademarkHydrovance.

Amounts of substituted urea, when used, in the composition of thisinvention range from 0.01 to 20%, and preferably, from 0.5 to 15%, andmost preferably, from 2 to 10% based on total weight of the compositionand including all ranges subsumed therein. Conventional humectants maybe employed in the present invention as skin benefit agent and inaddition to resorcinol and/or a derivative thereof. These are generallypolyhydric alcohol type materials. Typical polyhydric alcohols includeglycerol (i.e., glycerine or glycerin), propylene glycol, dipropyleneglycol, polypropylene glycol, polyethylene glycol, sorbitol,hydroxypropyl sorbitol, hexylene glycol, 1,3-butylene glycol, isopreneglycol, 1,2,6-hexanetriol, ethoxylated glycerol, propoxylated glyceroland mixtures thereof. Most preferred is glycerin, propylene glycol or amixture thereof. The amount of humectant employed may range anywherefrom 0.5 to 20%, preferably between 1 and 15% by weight of thecomposition.

When cationic ammonium compound and substituted urea are used, in a mostespecially preferred embodiment at least from 1 to 15% glycerin is used,based on total weight of the composition and including all rangessubsumed therein.

Compositions of the present invention may optionally include, along withresorcinol and/or derivative thereof, vitamins in addition to retinol(Vitamin A) present as a retinoic acid precursor. Illustrative vitaminsare Vitamin B₂, Vitamin B₃ (niacinamide), Vitamin B₆, Vitamin C, VitaminE, Folic Acid and Biotin. Derivatives of the vitamins may also beemployed. For instance, Vitamin C derivatives include ascorbyltetraisopalmitate, magnesium ascorbyl phosphate and ascorbyl glycoside.Derivatives of Vitamin E include tocopheryl acetate, tocopherylpalmitate and tocopheryl linoleate. DL-panthenol and derivatives mayalso be employed and Vitamin D and K are also options. Total amount ofoptional vitamins when present in compositions according to the presentinvention may range from 0.0 to 10%, preferably from 0.001 to 1%,optimally from 0.01 to 0.5% by weight of the composition.

Other optional additives suitable for use in this invention includealpha- and/or beta-hydroxyacids, 12-hydroxystearic acid, petroselinicacid, conjugated linoleic acid, creatine, creatinine, retinoid boosters(e.g., climbazole, bibonazole, farnesole, glycyrrchetinic acid, ursolicacid, geranyl geraniol, oleyl betaine, hexanoyl sphingosine) mixturesthereof or the like. Such additives, when used, collectively make upfrom about 0.001 to about 12% by weight of the composition.

Desquamation promoters may be present. Illustrative are thealpha-hydroxycarboxylic acids, beta-hydroxycarboxylic acids. The term“acid” is meant to include not only the free acid but also salts andC₁-C₃₀ alkyl or aryl esters thereof and lactones generated from removalof water to form cyclic or linear lactone structures. Representativeacids are glycolic and its derivatives, lactic and malic acids.Salicylic acid is representative of the beta-hydroxycarboxylic acids.Amounts of these materials when present may range from 0.01 to 15% byweight of the composition of this invention.

A variety of herbal extracts may optionally be included in compositionsof this invention. The extracts may either be water soluble orwater-insoluble carried in a solvent which respectively is hydrophilicor hydrophobic. Water and ethanol are the preferred extract solvents.Illustrative extracts include those from green tea, yarrow, chamomile,licorice, aloe vera, grape seed, citrus unshui, willow bark, sage, thymeand rosemary.

Also optionally suitable for use include materials like chelators (e.g.,EDTA), opacifiers (like TlO₂, particle size from 50 to 1200 nm, andpreferably, 50 to 350 nm), C₈-22 fatty acid substituted saccharides,lipoic acid, retinoxytrimethylsilane (available from Clariant Corp.under the SilCare IM-75 trademark), dehydroepiandrosterone (DHEA) andcombinations thereof. Ceramides (including Ceramide I, Ceramide 3,Ceramide 36 and Ceramide 6) as well as pseudoceramides may also beuseful. Amounts of these materials may range from 0.000001 to 10%,preferably from 0.0001 to 1% by weight of the composition of thisinvention.

Sunscreen actives may also be included in compositions of the presentinvention. Particularly preferred are such materials as ethylhexylp-methoxycinnamate, available as Parsol MCX, Avobenzene, available asParsol 1789 and benzophenone-3, also known as Oxybenzone. Inorganicsunscreen actives may be employed such as microfine titanium dioxide,octocrylene zinc oxide, polyethylene and various other polymers.

Amounts of the sunscreen agents when present may generally range from0.1 to 30%, preferably from 0.5 to 20%, optimally from 0.75 to 10% byweight.

Conventional buffers/pH modifiers may be used. These include commonlyemployed additives like sodium hydroxide, potassium hydroxide,hydrochloric acid, citric acid and citrate/citric acid buffers. In anespecially preferred embodiment, the pH of the composition of thisinvention is from 4 to 8, and preferably, from 4.25 to 7.75, and mostpreferably, from 6 to 7.5, including all ranges subsumed therein.

As previously noted, the SBA of the present invention can comprise inaddition to resorcinol and/or derivatives thereof, additional skinbenefit agents. It is preferred that resorcinol and/or derivativesthereof make up at least 25% by weight, and preferably, at least 40 to95% by weight, and most preferably, 100% by weight of the SBA.

Any oil soluble optional skin benefit agents or additives may, ifdesired, be provided collectively with the SBA to make up the portion ofthe skin benefit agent that is not resorcinol and/or a derivativethereof. Without being bound by theory, it is believed that the SBAstabilizes retinoic acid precursor by impeding the oxidation of the samein situ (i.e., in composition).

The composition of the present invention preferably is a leave-on skinlotion, cream, shampoo, conditioner, shower gel, antiperspirant,deodorant, depilatory, shave cream or toilet bar.

The invention of the present invention further relates to a method forimpeding oxidation of a RAP comprising the steps of combining, in noparticular order, the RAP and SBA in a carrier they are soluble in andrecovering a composition where oxidation of RAPs is impeded.

A wide variety of packaging can be employed to store and deliver thecomposition with stable retinoic acid precursors of this invention.Packaging is often dependent upon the type of personal care end-use. Forinstance, leave-on skin lotions and creams, shampoos, conditioners andshower gels generally employ plastic containers with an opening at adispensing end covered by a closure. Typical closures are screw-caps,nonaerosol pumps and flip-top hinged lids. Packaging forantiperspirants, deodorants and depilatories may involve a containerwith a roll-on ball on a dispensing end.

Alternatively these types of personal care products may be delivered ina stick composition formulation in a container with propel repelmechanism where the stick moves on a platform towards a dispensingorifice. Metallic cans pressurized by a propellant and having a spraynozzle serve as packaging for antiperspirants, shave creams and otherpersonal care products. Toilette bars may have packaging constituted bya cellulosic or plastic wrapper or within a cardboard box or evenencompassed by a shrink wrap plastic film.

The following examples are provided to facilitate an understanding ofthe present invention. The examples are not intended to limit the scopeof the claims.

EXAMPLES Example 1

Compositions were prepared with caprylic capric triglyceride as thecarrier to 100%. Storage was maintained at 45° C. Assessment of RAPamount in the formulae was achieved via HPLC using ASTM Standards.

Initial RAP Concentration (%) and Percent RAP Remaining (weeks) WeekWeek 4 20 Week Week Week % Week % RAP 0 1 4 Remaining 20 RemainingRetextra ®¹ 0.36 0.14 0 0 0 0 Retinyl Propionate 0.38 No 0.32 84 0 0Change Retinol 0.1 0.042 0.001 1 0 0 Retextra & ER² 0.33 No 0.24 73 0.0515 change Retinyl Propionate & ER 0.4 0.39 0.35 88 0.222 56 Retinol & ER0.1 0.087 0.01 10 0 0 ¹= made available by Molecular DesignInternational, hydroxyanasatil retinoate ²= ER denotes 4-ethylresorcinol, 0.35% in the composition which yellowed significantly slower(about 20% of the control based on visual inspection) when assessedafter being stored for 4 weeks at 45 degrees celcius.

The results show that 4-ethyl resorcinol improves the stability of theRAPs by preventing oxidation.

Example 2

The experiments in Example 2 were conducted in a manner that was similarto the one described in Example 1 except 4-hexyl resorcinol (HR) wasused as well. Resorcinol added at 0.35%. Caprylic capric triglyceridewas the carrier added to balance, 100%.

Week Week Week 0 1 4 Percent Remaining Con- Con- Con- Week Week Week RAPcentration centration centration 0 1 4 Retextra ® 0.36 0.14 0 100 100 73& ER Retextra ® 0.34 0.34 0.29 100 100 85 & HR Retinyl 0.38 0.38 0.32100 100 88 Propionate & ER Retinyl 0.37 0.37 0.37 100 100 100 Propionate& HR Retinol & ER 0.1 0.087 0.01 100 87 10 Retinol & HR 0.1 0.093 0.04100 93 40

The data provided demonstrates that the presence of resorcinolunexpectedly prevents the breakdown, oxidation of the RAP.

Example 3

The data provided in the experiments below demonstrate that when the SBAis present at a weight ratio of about 50% of the RAP, maximum stabilityis achieved.

Week 0 Week 1 Week 4 Ratio Con- Con- Con- RAP/SBA (weight %) centrationcentration centration Retinyl Propionate/ER 1:2 0.21 0.21 0.21 RetinylPropionate/ER 1:1 0.4 0.39 0.35 Retinyl Propionate/ER 2:1 0.44 0.42 0.42Retinyl Propionate — 0.38 0.38 0.32 Retinol/ER 1:3 0.1 0.09 0.01Retinol/ER 1:1 0.2 0.16 0.07 Retinol/ER 2:1 0.2 0.16 0.07 Retinol — 0.10.042 0.001

The invention claimed is:
 1. A composition comprising: (a) a retinoicacid precursor selected from retinyl propionate, hydroxyanasatilretinoate, and mixtures thereof; (b) a skin benefit agent selected from4-ethyl resorcinol, 4-butyl resorcinol, 4-hexyl resorcinol, 4-isopropylresorcinol and mixtures thereof; (c) niacinamide; and (d) a cosmeticallyacceptable carrier, wherein the retinoic acid precursor and the skinbenefit agent are present at a weight ratio of from about 1:2 to about2:1.
 2. The composition according to claim 1, wherein the retinoic acidprecursor is present from 0.001 to 10% by weight of the composition, andthe skin benefit agent is present from 0.001 to 10% of the composition.3. The composition according to claim 1 further comprising a retinoidbooster selected from climbazole, bibonazole, farnesol, glycyrrhetinicacid, ursolic acid, geranyl geraniol, oleyl betaine, hexanoylsphingosine, and mixtures thereof.
 4. The composition according to claim1 further comprises at least one component selected from creatine,1,2-octanediol, sunscreen, conjugated linoleic acid, hydroxyl acid,12-hydroxystearic acid, phenoxyethanol, glyceryl stearate, glycolstearate, stearamide AMP, PEG-100 stearate, cetyl alcohol, and mixturesthereof.
 5. The composition according to claim 1, wherein thecomposition is not an emulsion.
 6. The composition according to claim 1,wherein the composition is an oil-in-water emulsion.
 7. The compositionaccording to claim 1, wherein the composition is an water-in-oilemulsion.
 8. The composition according to claim 1, wherein the skinbenefit agent impedes oxidation of the retinoic acid precursor in thecomposition.
 9. A method for impeding oxidation comprising a step oftopically applying to skin the composition of claim 1.